Weeds between paving stones may well have an advantage – they reduce heat stress in cities, researchers in Santiago de Compostela found.
In the future, you would have a good reason to let weeds sprout unhindered in pavement or patio cracks. As an urban planner and botanist in Santiago de Compostela, Spain, have discovered, wild herbs in the joints can reduce the ambient temperature by up to 28 degrees Celsius. This finding could contribute to reducing heat stress in cities in the future.
"Weeds" conquer the city and produce a feel-good climate
+Not every herb has a positive effect on paving stones and the climate, but many cool the pent-up heat in cities.
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As the science magazine Spektrum.de reports, the urban planner and architect Ángel Panero made a discovery by chance while walking across the deserted square in front of the pilgrimage cathedral of Santiago de Compostela: The countless herbs that had conquered the pavement cracks of the otherwise piercingly hot square during the Corona lockdown suddenly created a veritable feel-good climate.
And the urban planner wondered whether it would not be possible to take advantage of this positive effect on the ecosystem by specifically reducing heat in cities, improving their water balance and, of course, preserving or increasing biodiversity. Inspired by this, botanists were commissioned to examine the different types of "weeds" on the square to see whether they damage the paving stones or bring predominant benefits. After all, there are differences between mosses and, for example, dandelions.
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Herbs bind water and provide oxygen
The scientists found that of the 44 species studied, many grasses, mosses and lichens protect the stones by having their roots in the joints connect the stones, thus increasing their stability. The even greater achievement, however, is that, according to Spektrum.de, the plants ensure a cooler climate – up to 28 degrees Celsius less were measured with a thermal imaging camera – bind water, store carbon dioxide and produce oxygen.
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According to Ángel Panero, if further experiments are promising, the findings can also be easily transferred to other building elements of the city, such as walls, and make an important ecological contribution in the future.
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